The present invention relates to an imaging apparatus for still picture or moving pictures to photograph photogenic subjects.
Imaging apparatuses using, as imaging devices, solid imaging devices such as CCD, CMOS and artificial retina chips have been used for still cameras or video cameras. Recently, in addition to the single device which has made photography a main purpose, an imaging apparatus capable of being installed in and connected to personal computers, portable information terminals or mobile phones is designed. When the characteristics of these information devices are considered, miniaturization of imaging apparatuses is a very important factor.
FIG. 14 shows a constitutional view of a conventional solid imaging system disclosed in e.g. Japanese Unexamined Patent Publication No. 227962/1998 and No. 293236/1998. In FIG. 14, 101 shows a photogenic subject, 102 an image formation lens to image the photogenic subject on the surface of an imaging device, 103 an imaging device having matrix-shaped photoelectric transfer devices to transfer to electric signals corresponding to optical intensity formed by an image 105 of photogenic subject imaged by image formation lens, and 104 a lens-barrel carrying the lens. Hereinbelow, filters such as low-pass filters and infrared filter are omitted in FIG. 14 for simplification.
Next, the operation is explained. A ray of light reflected by the photogenic subject 101 or generated by the photogenic subject 101 images the image 105 of the photogenic subject on the imaging device 103 by the image formation lens 102. Many photoelectric transfer devices are arranged on the imaging device 103, one photoelectric transfer device detects the optical intensity reaching a certain space and transfers light to electric signal corresponding to the optical intensity, and it is possible to reproduce the image of photogenic subject 105 imaged on whole of the imaging device on a display or the like by these electric signals and positional informations of arrangement of photoelectric transfer devices.
The brightness and the angle of field show the characteristics of optical system for imaging apparatuses. The brightness indicates a standard of brightness of the photogenic subject which can be photographed when the diaphragm is opened, and ordinarily F number indicates the brightness. When “a” shows the effective diameter of lens and “f” indicates the focal length of lens, the formula “F number=f/a” is given. Moreover, the angle of field indicates the field of the photogenic subject which can be photographed by the imaging system, that is, the field which the imaging device can stare through lens. For example, when the surface of the imaging device has the opposite angle b=½ inch (12.7 mm) and the shape is same as an ordinary television display having the hight and width in the ratio of three to four, the hight of the imaging device is (⅗)×b, and the width is (⅘)×b. When “L” (in the case of infinite focus, equal to approximately f) shows the distance from lens to the imaging device, the angle of field is given by the following formulasThe vertical angle of field=2×tan−1(((⅗)×b/2)/L)  (1)The horizontal angle of field=2×tan−1(((⅘)×b/2)/L)  (2)
Hereinbelow, assuming that a standard image formation lens for the imaging apparatus has F number of 2.8, and horizontal angle of field of 40°, the above formulas lead to f=13.96 mm, and a=4.98 mm. Therefore, the distance from the lens to the imaging device, that is, the thickness of the imaging apparatus is about 14 mm. On the other hand, the resolution of an image of the photogenic subject is determined by pixel pitches arranged in matrix-shape on the imaging device, and in the case of the imaging device having the opposite angle b=½ inch, to obtain an image having a width of 10.16 mm and VGA (640×480 pixels: the surface size of the imaging device shown in FIG. 13), the pixel pitch should be about 15.9 μm.
Now, FIG. 14 shows the resolution of a conventional imaging apparatus. In FIG. 14, X shows a position of the image formation lens, and Y an axis of the image formation lens. An arrow indicates the image and its size is 200 pixels. To explain simply, assuming that only the horizontal resolution is taken notice of and there is the photogenic subject having a width of 159 mm at a position of 698 mm from the lens, the distance L from the lens to the imaging device is 13.96 mm, so that the image of the photogenic subject will be reduced to 1/50 (13.96÷698) and be imaged on the imaging device. Accordingly, the size of the image of photogenic subject is 3.18 mm, and with respect to resolution, the image is read by the imaging device having 15.9 μm pitches, so that the image will be read by 200 pixels in the horizontal direction.
Since the conventional imaging apparatus has the above arrangement, the distance from the image formation lens to the light-receiving surface of imaging device must be long to gain a standard brightness and an angle of field, which makes imaging apparatuses thicker. Moreover, when the conventional imaging apparatus is installed to electronic machines, especially mobile phone machines, portable cameras, watches and portable information terminals, the size of these portable electronic machines becomes large because of a thick imaging system, and when connecting the conventional imaging apparatus to them, it is required to bring big imaging systems.
The present invention is made to solve the above problems, and an object thereof is to provide a thin-modeled imaging apparatus with a thin imaging device, and a thin-modeled electronic machine and portable electronic machine capable of mounting thereon an imaging apparatus.